Hi guys, I've spent the last couple of days working on my '07 XKR, one of the things I'm doing is refurbishing the brakes, replacing the R logos, changing the discs and pads etc...

Fronts went without a hitch, but I'm stuck on the rears because I can't retract the pistons on the rear calipers. I've done brakes on all the cars I've owned but this is the first time I've met calipers that need re-winding.

The old pads are quite worn (about 1/8" remaining), I did release the parking brake before starting work and got it apart OK but now obviously can't get the caliper back on with the much thicker new pads.

I've spent a few hours searching the forums and there seems to be two camps on this - one is that the caliper pistons just need rewinding, the other that it's not possible without the dealer diagnostic kit to retract the parking brake - what's the consensus on this? Can I get away with just buying a re-wind tool, or does this need the proper diagnostic kit?

I already know about the battery disconnect to re-calibrate the parking brake but I'm not sure whether I need to retract the brake actuator itself or can just re-wind the caliper pistons to get the extra room I need to get the caliper back in place.

I think the old girl is jealous that I still drive my old XJ Sport more :-)

 

I have not done the rear brakes on my Jags but, as far as reading previous posts, all you need is to rewind. A long nose pliars may do the job if you do not want to go to your local auto store for the special tool.

https://www.jaguarforums.com/forum/x...job-how-85582/

 

Here in the states we can usually borrow the rewind kit from a local autoparts store like Autozone. It fits in the caliper and has 2 pins that match the piston. All you need to do is turn the screw and it both forces and rotates the pistons into the caliper. As for the brake cable I don't know how that works so hopefully someone can chime in here and provide that info.

 

Thanks guys.

Yeah, I've managed to rotate the piston with a pair of needle nose pliers but not had any luck getting it to retract...going to try and get hold of a proper rewind tool later today.

Does anyone know if the threads are handed? To the pistons screw clockwise or anti-clockwise?

 

You need to (push) force the pistons while you rotate them. That is what the tool allows you to do. Also some calipers need clockwise rotation on one side and anti-clockwise rotation on the other side. Then again others go only one way. I know this didn't answer your question but hopefully someone who has done this will speak up.

 

Every rear caliper I'd ever handled thus far had a clockwise rotation for retracting. No guarantees that Jaguar is that way, however.

 

I've done my rear discs and pads a couple of times now. You want a Laser Tools brake caliper rewind tool (Amazon sell it, as do Halfords I think) and a Laser 4342 piston adapter (got mine from Amazon) which fits the dimples in the face of the piston. You'll need to attach the caliper back onto the carrier without the disc in place so you can use it, then slide the caliper back in to the wheel arch so you can get the plate wedged in to allow the rotating mechanism to push back against to put pressure into the piston while turning.

Both sides screw in the way clockwise, at least they do on my car. You'd be advised to undo the brake fluid reservoir cap before you start too, so the fluid you're displacing from the caliper can go somewhere. Having said that, I didn't lose any and didn't even find the level rose significantly but I used a turkey baster to remove a bit of fluid before I started, just in case. You can safely wind the piston all the way back in and it'll stop.

You can get a 17 or 19mm socket on the end of the tool to make it a bit easier to turn, I used a breaker bar. The pistons should rotate smoothly with a little force, if they're very stiff then the caliper may need replaced. Once you're finished and it's all back together and the car is on the floor again, pump the brake pedal a couple of times so it goes firm before starting the car.

Apologies if any of that was stating the obvious but I thought it worth including in case it's of use to someone else some day

 

Hey guys, thanks for the input. Turns out the issue was that the piston had slipped out of the adjuster and that combined with me doing this type of caliper for the first time and not wanting to use too much brute force in case it damaged the threads meant that the first one took me two evenings and the second took 15 minutes

8bit: yes both of mine wound in clockwise too, have wound them in just enough to get a loose fit with the new pads, will see how the handbrake resets tomorrow. I tried a dozen places to get something suitable, ended up with a Sealey VS0244. Had to grind a tad off of the pegs to get them down to 5mm but it had the correct 19mm centres on the pegs, basically tightened it up and turned it clockwise, letting the collar slip so it didn't push the piston too hard onto the adjuster before it had threaded properly, after that it was simple.

Will update when it's back on the road and working but seems OK so far

Cheers guys.

 

Cool, glad you got it sorted. Using the method I described earlier, and remembering to pressurise the system by pushing the pedal a couple of times before switching the engine on, I never had to reset the parking brake afterwards, just have to remember to leave the parking brake off. I found it much easier to wiggle the discs off and on with the car in N so the wheels turn freely.

It's pretty easy to check the brakes work OK, park the car with the front wheels chocked, leave the tranny in N and the parking brake off and kill the engine. Jack up one rear wheel, check it spins freely then push the pedal a couple of times then check the wheel is held fast. Drop the car back down, start the engine to depressurise the system then off again, then repeat the process on the other side. Back down, engine on again, apply the parking brake then engine off, then jack up each side in turn and check the wheels are held fast. That's basically what an MOT tester will do.

Again apologies if you know all this already but it might help someone doing this for the first time in the future.